Development and validation of a mathematical model for calculation surface pressure using a barometric pressure sensor in active wheelchair cushions: a pilot study on a single air cell

This paper presents the development of a mathematical model as an initial step toward calculating the surface pressure between a patient and an air-cell seat cushion, based on the barometric internal pressure of the cushion. The model was developed and validated using measurements from a single air cushion. A total of 36 measurement series were recorded under varying initial and ambient pressures. Each series included 11 force levels ranging from 50 to 150 N, applied to the air cushion using a controlled force test bench. Alongside the barometric internal and ambient pressures, the surface pressure was measured with a pressure plate from T&T medilogic Medizintechnik GmbH (Schönefeld, Germany). The barometric internal pressure was mathematically separated into two parameters: the initial internal pressure and the pressure difference induced by loading. Ten different functions were trained with half of the measurement series and validated with the other half, varying in complexity and parameter weighting. The best-performing model achieved an R²value of 0.98, with an average deviation of -1.9 ± 3.7% and a maximum error of 10.7%. These results are promising and comparable to the measurement accuracy of established pressure mat systems, supporting the model's potential as a foundation for future active wheelchair cushion applications.